Switch "mrc" and "mcr" commands to be toplevel ARM operations,
as they should initially have been.

Correct the usage message for both commands:  it matches ARM
documentation (as one wants!) instead of reordering them to
match the funky mrc() and mcr() method usage (sigh).

For Cortex-A8: restore a line that got accidentally dropped,
so the secure monitor mode shadow registers will show again.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>